The present invention relates in general to binocular construction, and in particular to a new and useful zoom mechanism for zoom binoculars.
The zoom binocular is a device in which the magnification can be changed during use by controlling a zooming lever. Some typical examples of zooming mechanisms for such binoculars are illustrated in FIG. 1 and FIG. 2.
The zooming mechanism shown in FIGS. 1 and 2 is constructed of the ring gears 01 and 02 which are concentric to eye lens (not shown), with intermediate gears 03 and 04 being engaged with respective ring gears 01 and 02 for idle rotation between the ring gears 01 and 02. A central gear 05 which is situated between the intermediate gears 03 and 04 and which is fitted for engagement with the intermediate gears 03 and 04, is coaxial with a machine shaft (not shown) about which the lens assemblies are pivotable. A zooming lever 06 is connected for rotating either of the ring gears 01 and 02 by 100 to 210 degrees.
FIG. 3 shows a publicly known example where a zooming service lever 2 has been fitted to a machine shaft 5', and this zooming mechanism functions to rotate a drive gear 7" which is coaxial to the drive shaft, by means of the zooming lever 2 moving around the center of the machine shaft. This rotates mirror symmetrical gears 12 and 12' fitted to internal cylinders 13 and 13' by turning a small gear 8 fitted to the lower face of a intermediate gear 9' on one side by means of this drive gear 7", thus providing the zooming function. In likewise fashion, gear 9" rotates due to the engagement of gear 11. Gears 9' and 9" are rotatable about shafts 10' and 10". Lever 2 rotates gear 7" which is fixed to shaft 4', by pivoting a post 6' which extends through a slot in the lever and which is fixed to shaft 4'.
The zoom mechanisms shown in FIG. 1 and FIG. 2, however, cannot be used for compact binoculars since the largely protruded zooming lever 06 must be fitted beneath the vane and moreover must be rotated by 100 to 210 degrees. In addition, if the attempt is made to reduce the rotary angle of 100 to 210 degrees, there may appear an unreasonable mechanical aspect as the screw spiral angle of an eye contact screw spiral cylinder is intensified, and further an unequal magnification will be elastically increased as the angle is intensified.
Secondly, although the zoom mechanism in FIG. 3 is suited for binoculars having a larger objective effective diameter, it cannot be applied to compact binoculars where the objective lens frames on the right and left sides are very close to each other because the central portion has no space for incorporating the control lever.